Previous studies in this laboratory have provided convincing evidence that mouse placenta contains stem cells which, under appropriate experimental conditions, will differentiate into mature erythrocytes and lymphocytes. The experiments were designed to provide information in relatively brief periods of time using highly artificial conditions to ensure definitive results. The studies for which support is being sought will stress therapeutic approaches to clinical conditions resembling human disease. The "W" anemia in mice, a genetic type of hypoplastic anemia, has been selected for our initial efforts. Pilot studies have already shown the effectiveness of placenta in this experimental situation. This model will be used to study such features as: 1. Which cells are responsible for the beneficial effects. 2. The possible advantages of "early" over term placenta. 3. Rejection problems with allogenic placenta. 4. The long-range effects of placental implants. If time permits, other "clinical" conditions will be explored and attempts will be made to extend the observations to other animal species. The eventual goal is to determine if the placenta may serve as a virtually unlimited source of hematopoietic cells which may be used to treat such conditions as marrow hypoplasia following intensive anti-cancer treatment. Some of those features that contribute to the success of the placenta as a "transplant" during pregnancy may be helpful in this clinical situation.